documentation: add FAQ entry concerning serial port configuration

    <h2 id="faq">Frequently asked questions</h2>

    <ul>

      <li><a href="#faq-boot-hangs">The boot hangs

      after <code>Starting network...</code></a></li>

    </ul>

    <h3 id="faq-boot-hangs">The boot hangs after <code>Starting

    network...</code></h3>

    <p>If the boot process seems to hang after the following messages

    (messages not necessarly exactly similar, depending on the list of

    packages selected):</p>

    <pre>Freeing init memory: 3972K

Initializing random number generator... done.

Starting network...

Starting dropbear sshd: generating rsa key... generating dsa key... OK</pre>

    <p>then it means that your system is running, but didn't start a

    shell on the serial console. In order to have the system start a

    shell on your serial console, you have to go in the Buildroot

    configuration, <code>Target options</code>, enable <code>Generic

    serial port config</code>, and select the serial port and speed

    you would like to use for the shell. This will automatically tune

    the <code>/etc/inittab</code> file of the generated system so that

    a shell starts on the correct serial port.</p>

    <h2 id="links">Resources</h2>

    <p>To learn more about Buildroot you can visit these websites:</p>